vertical mining rate
31steel — steellike, adj. /steel/, n. 1. any of various modified forms of iron, artificially produced, having a carbon content less than that of pig iron and more than that of wrought iron, and having qualities of hardness, elasticity, and strength varying …
32Nevada — This article is about the U.S. state of Nevada. For other uses, see Nevada (disambiguation). State of Nevada …
33Ocean thermal energy conversion — Temperature differences between the surface and 1000m depth in the oceans Ocean Thermal Energy Conversion (OTEC) uses the difference between cooler deep and warmer shallow or surface ocean waters to run a heat engine and produce useful work,… …
34Medieval technology — Pumhart von Steyr, a 15th century supergun …
35United States — a republic in the N Western Hemisphere comprising 48 conterminous states, the District of Columbia, and Alaska in North America, and Hawaii in the N Pacific. 267,954,767; conterminous United States, 3,022,387 sq. mi. (7,827,982 sq. km); with… …
36Environmental impact of wind power — Livestock ignore wind turbines,[1] and continue to graze as they did before wind turbines were installed. Compared to the environmental impact of traditional energy sources, the environmental impact of wind power is relatively minor. Wind power… …
37Germany — /jerr meuh nee/, n. a republic in central Europe: after World War II divided into four zones, British, French, U.S., and Soviet, and in 1949 into East Germany and West Germany; East and West Germany were reunited in 1990. 84,068,216; 137,852 sq.… …
38Russia — /rush euh/, n. 1. Also called Russian Empire. Russian, Rossiya. a former empire in E Europe and N and W Asia: overthrown by the Russian Revolution 1917. Cap.: St. Petersburg (1703 1917). 2. See Union of Soviet Socialist Republics. 3. See Russian… …
39Economic history of Brazil — The economic history of Brazil covers various economic events and traces the changes in the Brazilian economy over the course of the history of Brazil. Portugal, which first colonized the area in the 16th century, enforced a colonial pact with… …
40Marcellus Formation — Stratigraphic range: Middle Devonian …
